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Blood–brain barrier characteristics are analyzed, which must be considered to be much more than a connective supporting tissue between the neurons and the capillary endothelium.

ESA (ESA ILSRA-2009-1026); ASI (contract no. 5681); Regione Toscana (POR FSE 2007-2013-FORTEC); Kayser Italia; Lions Club International, District 108LA, Toscana, Italy.

The establishment of effective vascularization is a key challenge in regenerative medicine. To achieve this, the transplantation of native microvascular fragments has emerged as a promising novel concept. Microvascular fragments can be isolated in large amounts from fat tissue, exhibit a high angiogenic activity, and represent a rich source of mesenchymal stem cells. Originally, microvascular fragments have been used in angiogenesis research for the isolation of capillary endothelium and for functional sprouting assays. More recent studies have demonstrated that they rapidly develop into microvascular networks after transfer into tissue defects. Moreover, they are suitable for the generation of prevascularized tissue constructs. Hence, a wide range of future medical applications may benefit from the use of these natural vascularization units.

Although the pulmonary capillaries were discovered in 1661, the ultrastructure of the wall was not elucidated until 60 years ago. Electron micrographs then showed that only 0.2 μm of tissue separated the capillary endothelium from the alveolar space over much of the area. In retrospect this vanishingly small protective layer should have alerted physiologists to the potential fragility of the capillaries, but this was not appreciated until almost 40 years later. This predicament is unique to pulmonary capillaries. No other capillaries in the body are shielded from the outside environment by such a minute amount of tissue. Reasons why the fragility of the capillaries was not recognized earlier include an inappropriate comparison with the properties of systemic capillaries, the mistaken view that the pulmonary capillary pressure is always low, and a misleading use of the Laplace equation. Evidence for the fragility comes from physiological, pathological, and laboratory observations. As expected from evolutionary considerations, the fragility only becomes evident in the normal lung under exceptional conditions. These include elite human athletes at maximal exercise and animals that have developed the capacity for extreme aerobic activity. However, lung and heart diseases frequently cause capillary disruption. Remodeling of pulmonary capillaries occurs in humans in whom the capillary pressure rises over a long period. Neonatal capillaries are extremely fragile, presumably because they have never been exposed to increased transmural pressures. The capillaries conform to the general biological rule that tissue adapts its structure to carry out its required function.

Brain, the center of the nervous system in all vertebrate, plays the most vital role in every function of human body. However, many neurodegenerative diseases, cancer and infections of the brain become more prevalent as populations become older. In spite of the major advances in neuroscience, many potential therapeutics are still unable to reach the central nervous system (CNS) due to the blood – brain barrier (BBB) which is formed by the tight junctions within the capillary endothelium of the vertebrate brain .This results in the capillary wall behaving as a continuous lipid bilayer and preventing the passage of polar and lipid insoluble substances. Several approaches for delivering drugs to the CNS have been developed to enhance the capacity of therapeutic molecules to cross the BBB by modifying the drug itself, or by coupling it to a vector for receptor-mediated, carrier mediated or adsorption-mediated transcytosis. The current challenge is to develop drug delivery systems that ensure the safe and effective passage of drugs across the BBB. This review focuses on the strategies and approaches developed to enhance drug delivery to the CNS.

Summary An ultramicroscopic study of early lesions in experimentally produced pneumonia in two pigs induced by intranasal inoculation of Haemophilus pleuropneumoniae serotype 1, was performed. Samples were obtained at 24 hours and 48 hours post-inoculation (p. i.). Both types of epithelial cells showed marked degenerative changes of a non-specific nature 24 hours p.i. The capillaries were dilated and filled with packed erythrocytes in different stages of disintegration. At 24 hours p. i. only slight degenerative changes were found in the capillary endothelium, while at 48 hours degenerative changes were a regular finding. The thrombi formed in the capillaries and identified in the light microscope as appearing to consist of fibrin were in fact composed of disintegrated erythrocytes. The vascular changes found in the initial stages had similarities with the Shwartzman reaction. The inflammatory cells found in connection with the degenerative and exudative changes were identified as macrophages and occasional neutrophils. The pathogenesis of the ultrastructural changes induced by Haemophilus pleuropneumoniae is discussed, based on our results as well as those reported in the literature. Zusammenfassung Pleuropneumonie der Schweine durch Haemophilus pleuropneumoniae III. Elektronenmikroskopische Studie Fruhe Lasionen einer Pneumonie beim Schwein, experimentell durch intranasale Inokulation mit Haemophilus pleuropneumoniae Serotyp I induziert, wurden elektronenmikroskopisch untersucht. Untersuchungsproben wurden nach 24 und 48 Stunden gewonnen. Die Kapillaren waren erweitert und mit Erythrozyten in verschiedenen Stadien der Auflosung gefullt. 24 Stunden nach der Inokulation liesen sich nur leichte degenerative Veranderungen am Kapillarendothel feststellen, wahrend nach 48 Stunden Degenerationen die Regel waren. Die in den Kapillaren entstandenen Thromben, lichtmikroskopisch als fibrinos gedeutet, setzten sich aus aufgelosten Erythrozyten zusammen. Die Gefasveranderungen in den Anfangsstadien ahnelten der Shwartzman-Reaktion. Die in Verbindung mit den degenerativen und exudativen Veranderungen auftretenden Entzundungszellen wurden als Makrophagen und gelegentliche Neutrophile identifiziert. Die Pathogenese der durch Haemophilus pleuropneumoniae hervorgerufenen ultra-strukturellen Veranderungen werden aus der Basis eigener Ergebnisse sowie der vorliegenden Literatur diskutiert. Resume Pleuropneumonie du porc due a Haemophilus pleuropneumoniae III. Etude au microscope electronique Les lesions precoces d'une pneumonie chez le pore induite experimentalement par inoculation intranasale d'Haemophilus pleuropneumoniae serotype I ont ete examinees au microscope electronique. Les echantillons ont ete preleves apres 24 et 48 heures. Les capillaires etaient elargis et remplis d'erythrocytes a differents stades de lyse. Seules de legeres lesions degeneratives de l'endothelium capillaire ont ete mises en evidence 24 heures apres l'inoculation alors que des degenerescences furent la regle apres 48 heures. Les thrombus constates dans les capillaires, caracterises de fibrineux au microscope optique, se composaient d'erythrocytes lyses. Les lesions vasculaires ressemblaient au debut a la reaction de Shwartzman. Les cellules inflammatoires en liaison avec les lesions degeneratives et exsudatives ont ete identifiees comme des macrophages et parfois des neutrophiles. La pathogenese des lesions ultrastructurelles dues a Haemophilus pleuropneumoniae est discutee sur la base de ces resultats et de la litterature existante. Resumen Pleuropneumonia porcina producida por Haemophilus pleuropneumoniae III. Estudio con el microscopio electronico Al microscopio electronico se estudiaron las lesiones precoces de una pneumonia en porcinos, inducida por via experimental mediante inoculacion intranasal con Haemophilus pleuropneumoniae serotipo I. Las muestras a examinar se obtuvieron al cabo de 24 y 48 horas. Los capilares se hallaban dilatados y llenos de eritrocitos empacados en estadios diferentes de desintegracion. 24 horas despues de la inoculacion se hallaron solo cambios degenerativos ligeros en el endotelio capilar, mientras que a las 48 horas los cambios degenerativos eran un hallazgo regular. Los trombos formados en los capilares e identificados al microscopio electronico como fibrinosos estan compuestos, de hecho, por eritrocitos desintegrados. Los cambios vasculares hallados en los estadios iniciales tienen semejanzas con la reaccion de Shwartzman. Las celulas inflamatorias encontradas en conexion con los cambios degenerativos y exudativos fueron identificadas como macrofagos y ocasionalmente neutrofilos. Se discute la patogenia de los cambios ultraestructurales inducidos por Haemophilus pleuropneumoniae, basandonos en nuestros resultados asi como en los hallados en la bibliografia.

Objective— Emerging evidence suggests that human blood contains bone marrow (BM)-derived endothelial progenitor cells that contribute to postnatal neovascularization. Clinical trials demonstrated that administration of BM-cells can enhance neovascularization. Most studies, however, used crude cell populations. Identifying the role of different cell populations is important for developing improved cellular therapies. Methods and Results— Effects of the hematopoietic stem cell–containing CD34 + cell population on migration, proliferation, differentiation, stimulation of, and participation in capillary-like tubule formation were assessed in an in vitro 3-dimensional matrix model using human microvascular endothelial cells. During movement over the endothelial monolayer, CD34 + cells remained stuck at sites of capillary tube formation and time- and dose-dependently formed cell clusters. Immunohistochemistry confirmed homing and proliferation of CD34 + cells in and around capillary sprouts. CD34 + cells were transduced with the LNGFR marker gene to allow tracing. LNGFR gene–transduced CD34 + cells integrated in the tubular structures and stained positive for CD31 and UEA-1. CD34 + cells alone stimulated neovascularization by 17%. Coculture with CD34 − cells led to 68% enhancement of neovascularization, whereas CD34 − cells displayed a variable response by themselves. Cell–cell contact between CD34 + and CD34 − cells facilitated endothelial differentiation of CD34 + cells. Conclusions— Our data suggest that administration of CD34 + -enriched cell populations may significantly improve neovascularization and point at an important supportive role for (endogenous or exogenous) CD34 − cells.

Understanding the relationship of the structure of organs to their function is a key component of integrative physiological research. The structure of the organs of the body is not constant but changes, both during growth and development and under conditions of sustained stress (e g. high altitude exposure and disease). Recently, powerful new techniques have become available in molecular biology, which promise to provide novel insights into the mechanisms and consequences of these altered structure-function relationships. Conventionally structure-function relationships are studied by microscopic examination of tissue sections. However, drawing conclusions about the three-dimensional structure of an organ based on this two-dimensional information frequently leads to serious errors. The techniques of stereology allow precise and accurate quantification of structural features within three-dimensional organs that relate in a meaningful way to integrated function. For example, knowledge of changes in the total surface area of the capillary endothelium in a n organ can be related directly to changes in fluid filtration and permeability, or knowledge of total vessel length and mean radius allows deductions about vascular resistance. Confocal microscopy add s enormously to the power of stereological approaches. It reduces the difficulties and labour involved in obtaining suitable images. Moreover, when used in conjunction with new analytical software, it allows convenient application of stereology to small samples and those in which it is essential to maintain a specific orientation for interpretation. The information obtained will allow us to examine in a quantitative manner the altered structure-function relationships produced by manipulation of single genes and regulatory pathways in whole organisms.

Gas exchange is the vital function of the lungs. It occurs in the alveoli, where oxygen and carbon dioxide diffuse across the alveolar epithelium and the capillary endothelium surrounding the alveoli, separated only by a fused basement membrane 0.2-0.5 μm in thickness. This tenuous barrier is exposed to dangerous or innocuous particles, toxins, allergens and infectious agents inhaled with the air or carried in the blood. The lung immune system has evolved to ward off pathogens and restrain inflammation-mediated damage to maintain gas exchange. Lung-resident macrophages and dendritic cells are located in close proximity to the epithelial surface of the respiratory system and the capillaries to sample and examine the air-borne and blood-borne material. In communication with alveolar epithelial cells, they set the threshold and the quality of the immune response.

Many potential CNS active agents, including peptides, proteins, antibodies, and gene medicines, do not readily enter brain from blood, owing to poor permeability through the blood-brain barrier (BBB). The successful delivery of these agents through the BBB in vivo is closely linked to knowledge of pharmacokinetics and transport mechanism at the brain capillary endothelium. In this review, we discuss brain delivery strategies of peptides and proteins from view points of pharmacokinetics and BBB transport mechanism. In addition, this review summarizes recent information regarding the transport system of peptides and proteins. Furthermore, some novel technologies for BBB delivery strategies are introduced in the last part of the review.

Murine methylcholanthrene A–induced (meth A)1 fibrosarcomas, which exhibit spontaneous vascular insufficiency manifested by a heterogeneous pattern of thrombohemorrhage and central necrosis, as well as a failure to form metastatic lesions 12, provide an ideal starting point for isolation of tumor-derived mediators that perturb the vasculature 3456. We purified a novel cytokine-like molecule, endothelial-monocyte activating polypeptide (EMAP) II, from meth A–conditioned medium based on its capacity to induce activation of endothelial cells (ECs) and mononuclear phagocytes 56. This single chain polypeptide, devoid of a signal sequence, is initially synthesized as an ≈34-kD intracellular precursor, which is processed to the mature ≈20-kD form and released extracellularly by an as yet unidentified pathway. EMAP II showed no significant homology to other known proteins such as cytokines or growth factors. However, an aspartic acid residue is present in the P-1 position in both murine and human EMAP II, suggesting that a cysteine protease in the IL-1β–converting enzyme family might be responsible for producing mature EMAP II from its pro-form. Our initial characterization of EMAP II suggested that its properties resembled those of proinflammatory mediators. For example, EMAP II induced endothelial release of von Willebrand factor, translocation of P-selectin to the cell surface, and synthesis and expression of E-selectin and procoagulant tissue factor 56; these, and EMAP II–mediated activation of cultured monocytes, resulting in production of cytokines and stimulation of cell migration, suggested phlogogenic properties. However, EMAP II administered in vivo, locally or systemically, gave rise to, at most, mild and transient inflammation 6, suggesting that its effects were quite different from those of TNF or IL-1 278. In this study we report that EMAP II has antiangiogenic properties preventing blood vessel ingrowth in two experimental angiogenesis models, and suppressing the growth of primary and metastatic tumors without toxicity in normal organs. Consistent with this hypothesis, EMAP II appears to target growing ECs; exposure of growing cultured capillary endothelium to EMAP II induces apoptosis, which is magnified by concomitant hypoxia. These data suggest that EMAP II is a polypeptide with antiangiogenic properties that targets rapidly growing vascular beds.

The capillary endothelium of the brain and spinal cord possesses tight junctions and, thus, behaves as a continuous lipid bilayer that prevents the passage of highly polar and lipid-insoluble substances. Highly active enzymes expressed in the brain endothelial cells and cerebral pericytes also represent a metabolic component that contributes to the homeostatic balance of the central nervous system (CNS). Peptides cannot enter the brain and spinal cord from the circulating blood because they are highly polar and lipid insoluble, metabolically unstable, and generally do not have active transport systems in this membranous barrier. Hence, the blood-brain barrier (BBB) is the major obstacle to peptide-based therapeutics that are potentially useful for combating diseases affecting the central nervous system. The article discusses invasive, physiological-based and chemical-enzymatic approaches to overcome the BBB by reviewing both primary and patent literature.

Light and election microscopy were used to document the degree of renal corpuscle development in boreal telcost fishes that produce peptide or glycopeptide antifreeze compounds on a seasonal or permanent basis. Emphasis was placed on gadids, cottids and pleuronectids from both the North Atlantic and North Pacific Oceans. Based on the classification of Marshall and Smith (1930), corpuscle development ranged from fully glomerular (Type 1) to pauciglomerular (Type III). Unlike the situation in Antarctic notothenioid fishes, there were no aglomerular species among the boreal fishes. Corpuscles were small in diameter in gadids whereas in cottids they ranged from small to large with considerable intraspecific variation. Eight of eleven species with antifreeze had intermediate (Type II-III) or pauciglomerular kidneys with relatively few dense corpuscles (dia. 36-82μm). In some of these species an extensive mesangium and a substantial capillary endothelium contributed to a glomerular filtration barrier that was four to five times thicker than that in Type I kidneys. The corpuscles of other pauciglomerular species were unremarkable and appeared functional at the ultrastructural level. The boreal fish fauna is taxonomically diverse and, compared to the unrelated Antarctic fauna, of relatively recent evolutionary origin. Furthermore, antifreeze is present only during the winter in some species. Hence it is not surprising that the urinary conservation of antifreeze is accomplished by mechanisms other than the evolutionary loss of renal corpuscles.

Before dairy cow feed evaluation can progress from systems based on empirical measurement to those based on mechanistic modelling the essential components of the model have to be defined. This review describes those elements which pertain to the mammary gland itself, briefly describing the major metabolic events within the gland before considering the supply of substrates to the udder and the uptake of those substrates across the capillary endothelium and basolateral membrane of the secretory cell. A level of complexity is revealed which throws into question our ability to construct adequate mechanistic models without considerably more input into understanding the fundamental biology of the mammary gland.

The natural anticoagulant pathway involving heparan sulfate proteoglycan and antithrombin III (ATIII) was studied in serial biopsies from 90 cardiac allograft recipients. The ATIII component of this pathway was identified immunocytochemically on venous endothelium and arterial smooth muscle cells and intima of normal donor hearts and stable allografts. Unstable grafts lacked vascular ATIII and contained fibrin deposits. Neither stable nor unstable grafts had ATIII-reactive capillary endothelium. Grafts with absent vascular ATIII could (1) result in death, (2) revert to an arterial/venous ATIII distribution or (3) develop ATIII-reactive capillary endothelium. The development of ATIII-reactive capillaries was associated with a survival advantage, and such reactivity seemed to be promoted by heparin.

Lankesterella poeppigii n. sp. is described from Bufo poeppigii (Tschudi, 1845) from Peru. Merogony and oogony occur in the capillary endothelium and the macrophages in the liver, spleen and kidneys. Meronts are oval, 25,2–29,4 x 15,7–16,8 μm in size and yield 35–46 merozoites. Oocysts are 26,3–29,4 x 15,1–17,6 μm in size; sporozoites 9,2-9,8 x 4,2–5,0 μm in size, assemble in macrophages. Released 8,7–9,8 x 2,8–3,1 μm sporozoites enter erythrocytes. L. poeppigii is compared with Lankesterella petiti Lainson & Paperna, 1995 infecting Bufo marinus (Linnaeus, 1758) in Brazil. The above mentioned specific characters, added to differences in hosts and geographical location warrant the description of Lankesterella poeppigii from B. poeppigii as a new species., Lankesterella poeppigii n. sp. es descrita de Bufo poeppigii (Tschudi, 1845) del Perú. La merogonia y oogonia se producen en el endotelio capilar y los macrófagos en el hígado, el bazo y los riñones. Los esquizontes son ovalados, 25,2–29,4 x 15,7–16,8 micras de tamaño y producen 35–46 merozoitos. Los ooquistes miden 26,3–29,4 x 15,1–17,6 micras de tamaño; esporozoitos, reunidos en los macrófagos, miden 9,2-9,8 x 4,2-5,0 micras de tamaño. Liberados, los esporozoitos miden 8,7–9,8 x 2,8–3,1 micras y entran en los eritrocitos. Lankesterella poeppigii es comparada con L. petiti Lainson y Paperna, 1995, que infecta a Bufo marinus (Linnaeus, 1758) en Brasil. Los caracteres específicos citados, sumados a las diferencias entre los huespédes y en la localización geográfica justifican la clasificación de la Lankesterella de B. poeppigii como una nueva especie.

Pulmonary intravascular macrophages (PIMs) are an extensive population of mature phagocytic cells adherent to the pulmonary capillary endothelium in selected species. They are not prevalent in lungs of commonly studied laboratory animals, such as rodents, and thus have only been recently appreciated. However, their potential role in host defense and acute lung injury has attracted interest, since a number of studies have demonstrated pulmonary localization of circulating particles, microbes, and endotoxin by PIMs. Those animal species, such as ruminants, that provide useful models of pathogen (or endotoxin)-induced acute lung injury demonstrate rapid pulmonary uptake of bacteria by PIMs. Inflammatory mediators released by activated PIMs may initiate the process and provoke accumulation of neutrophils and platelets. This review summarizes the morphological characteristics of PIMs and their species distribution. The role of these members of the mononuclear phagocyte system, both beneficial and potentially pathogenic, is reviewed. The question of whether PIMs have a role in acute lung injury in humans is also discussed.

Morphometric analysis of electron micrographs of the eel rete mirabile revealed that pericytes occupied nearly one-third of the cellular volume of this organ with over 75% of the pericyte volume associated with arterially derived capillaries. These pericytes were highly arborized, extending processes which encircled the capillaries and covering, on average, more than 85% the ablumenal surface of arterially derived capillaries. Pericytes and endothelial cells interacted in a manner suggesting that pericyte activity modulates both capillary blood flow and permeability.

Objective - Emerging evidence suggests that human blood contains bone marrow (BM)-derived endothelial progenitor cells that contribute to postnatal neovascularization. Clinical trials demonstrated that administration of BM-cells can enhance neovascularization. Most studies, however, used crude cell populations. Identifying the role of different cell populations is important for developing improved cellular therapies. Methods and Results - Effects of the hematopoietic stem cell-containing CD34+ cell population on migration, proliferation, differentiation, stimulation of, and participation in capillary-like tubule formation were assessed in an in vitro 3-dimensional matrix model using human microvascular endothelial cells. During movement over the endothelial monolayer, CD34+ cells remained stuck at sites of capillary tube formation and time- and dose-dependently formed cell clusters. Immunohistochemistry confirmed homing and proliferation of CD34+ cells in and around capillary sprouts. CD34+ cells were transduced with the LNGFR marker gene to allow tracing. LNGFR gene-transduced CD34 + cells integrated in the tubular structures and stained positive for CD31 and UEA-1. CD34+ cells alone stimulated neovascularization by 17%. Coculture with CD34- cells led to 68% enhancement of neovascularization, whereas CD34- cells displayed a variable response by themselves. Cell-cell contact between CD34+ and CD34- cells facilitated endothelial differentiation of CD34+ cells. Conclusions - Our data suggest that administration of CD34+-enriched cell populations may significantly improve neovascularization and point at an important supportive role for (endogenous or exogenous) CD34- cells. © 2005 American Heart Association, Inc. Chemicals / CAS: nitric oxide, 10102-43-9; Antigens, CD34; Biological Markers

The fine structure of the conus medullaris of the spinal cord and surrounding structures were studied in postnatal developing rats, with special attention being paid to the vasculature. The most striking finding was the presence of fenestrae in the capillary endothelium of the subarachnoid space. These structures were not obvious in adult rats. The fenestrated capillaries may influence fluid dynamics in the subarachnoid space of the spinal cord at the level of the conus medullaris, during early stage of postnatal development.

The blood-brain barrier (BBB) continues to intrigue and frustrate neuroscientists. Perhaps like no other organ, the brain, together with its BBB challenges, the investigator at a number of levels. This is certainly true at the basic science level in elucidating the mechanisms by which it regulates the microenvironment of the central nervous system, allowing the control and transport of D-glucose, certain amino acids, ions and peptides by selective, saturable and often stereo-specific carrier systems. These systems support cerebral metabolism, neurotransmitter and protein synthesis, and maintain the extracellular environment of the brain to allow it to function under optimal conditions despite wide fluctuations in the environment of the rest of the body. The high metabolic component of the cerebral capillary endothelium, constituting the enzymatic element of the BBB, likewise interests the basic scientist in elucidating the mechanisms by which it separates and protects the brain from a variety of neurotransmitters, hormones and endogenous messengers that possess one role in the periphery and another in brain. Additionally, the manner in which the structural and enzymatic components of the BBB interact to so ably protect the brain from exogenous toxins continues to capture our attention. In as much as the BBB protects and regulates the microenvironment of the brain to allow it to function optimally under diverse conditions during health, it is frustrating from a clinical viewpoint that these same mechanisms thwart our ability to intervene during disease, impeding us in our corrective measures. Specifically, it limits our ability (i) to deliver chemotherapeutic agents, such as during the treatment of infections and cancer, and (ii) to selectively manipulate levels of neurotransmitters and neuropeptides and enzymes, such as in the treatment of Parkinson’s and Alzheimer’s diseases.

A detailed correlative morphologic description using light microscopy (LM), transmission electron microscopy (TEM) and high resolution SE-I scanning electron microscopy (SEM) was conducted on the capillary endothelium of the zona-fasciculata (Z-F) in juvenile male rhesus monkeys. The glucocorticoid synthesis and release phenomena, associated with stress stimulated release of adrenocorticotropic hormone (ACTH) via the hypothalamic-pituitary axis, intimately involves capillaries of the Z-F. A comprehensive study of all the ultrastructural features implicated in the transendothelial uptake of steroidogenic precursors and release of glucocorticoids in perfused rhesus adrenals has not previously been made. This report presents correlative images of transendothelial openings that include previously described single diaphragmed fenestrae and plasmalemma vesicles, and double diaphragmed transendothelial channels. New observations of endothelial cell pockets, tight junctional complexes and membrane filled ghost sacs were recorded from perfused rhesus adrenal. Membranous ghosts associated with adrenocortical endothelium were reported in a previous TEM study of perfused rat, however the potential argument existed that ghosts were artifactual. Their role as steroid hormone releasing structures remains an open question, yet their structural characteristics appear justified based on imaging of identical profiles observed in perfused rhesus adrenocortical specimens. These structural features are considered for the potential of gating and sorting of metabolites, and release of glucocorticoids in response to ACTH stimulated stress events.

In previous publications (1,2) the hypothesis was put forward that atheroma is caused by some pathogen or metabolic fault which impairs the transportability of cholesterol in the plasma. The lipoproteins containing the faulty metabolites are assumed to be incapable of traversing the capillary endothelium and continue to circulate uselessly in the blood stream, possibly giving rise to hypercholesterolaemia, until captured by lipophages which, if they can successfully complete their journey, void them into the gall bladder. The present paper takes the argument a step further by pointing out that the types of substances most likely to cause the described impairment are surfactants. A surfactant finding its way into the plasma could separate cholesterol from its carrier protein and itself become its carrier. The complex would still be kept in suspension in the plasma, but unable to cross biological barriers like the capillary endothelium. An important argument in favour of the hypothesis is that it can offer an explanation of the long-standing medical mystery of the connection between atheroma and the hardness or softness of the water supply. Infant deaths from coronary occlusion present a similar enigma. The paper points out that surfactants can conceivably find their way into infants' feeding bottles.

A fine structural investigation of the transport of intravenously-injected ferritin (110 A) through the external vascular barrier (choriocapillaris and Bruch's membrane) of the Japanese quail retina has been sequentially detailed. One minute after injection ferritin is found mainly within the vascular lumina of the choriocapillaris but also is seen in pinocytic vesicles within the capillary endothelium and dispersed throughout the various components of Bruch's membrane. Ferritin transport through the capillary endothelium appears to occur via pinocytic vesicles in the thickened portions and diaphragmatic pores (single and double) in the attenuated areas. Within 5–10 min post-injection ferritin is observed within the basal infoldings of the pigment epithelium.

The number of cytoplasmic vesicles in the capillary endothelium was determined by ultrastructural morphometry and correlated with the uptake of technetium-99m pertechnetate used in brain scintigraphy. Ten gliomas were studied for uptake rates of 99mTc pertechnetate. Three gliomas from the different groups of uptake rates were quantitatively analyzed for cytoplasmic vesicle content. Capillaries of tumors without uptake had a low content of cytoplasmic vesicles, which was similar to that obtained in normal brain control. In tumors with low and moderate uptake rates, the cytoplasmic vesicles content increased significantly (p less than 0.05) by about 300% and 400%, respectively, as compared with that found in impermeable tumor and in normal brain. The correlation found between the cytoplasmic vesiculation of the endothelial cells in gliomas' capillaries and the uptake of 99mTc pertechnetate suggests that pinocytosis might be a factor in the uptake of the radionuclide. The present findings might be applicable to treatment with hydrophilic chemotherapeutic agents in moderate and highly permeable tumors.

Selected formalin-fixed, paraffin-embedded tissues of human and canine fucosidosis were stained with nine different lectins. Neurons, splenic sinusoidal cells, hepatic Kupffer cells, tissue macrophages, and capillary endothelium from human patients with fucosidosis stained intensely with Ulex europaeus agglutinin-I (UEA-I), but the same cells were unstained in tissues from canine fucosidosis. Since UEA-I specifically binds to terminal fucose residues, and fucose-rich undegraded metabolites are stored in affected cells of both human and canine fucosidosis, the variable lectin staining pattern demonstrates an unexpected species-specific histochemical variability. This finding highlights the fact that although both species have decreased fucosidase activity, the precursor substrates, undegraded stored metabolites, and particular cells affected by this enzyme deficiency are different.

It has been proposed that γ-glutamyl transpeptidase (GGTP) is involved in amino acid transport across the blood-brain barrier. A controversy exists, however, about whether or not sufficient GGTP activity is present in chick brain capillaries to be demonstrated histochemically. Under conditions in which GGTP was readily demonstrated in chick kidney, hamster kidney, and hamster brain capillaries, no GGTP activity was present in chick brain capillaries. Therefore, it is unlikely that GGTP activity is present in sufficient quantity in chick brain capillaries to account for all amino acid transport across the blood-brain barrier.

Pinocytotic vesicles are one of several anatomic factors relevant to the permeability for macromolecules of capillary endothelia. We quantitified the number and distribution of pinocytotic vesicles present in the endothelium of pulmonary capillaries. Several similar studies have been reported in the past for endothelia of systemic capillaries, but the technical difficulties involved in this difficult application of morphometry never have been discussed. In the present work, an on-line microprocessor was used to assist with the processing of the point-counting data. The average figures from nine rabbit lungs for parameters thought to be relevant to characterize the population of vesicles are: thickness of the endothelium (TAUen) 0.192 microns; number of vesicles per volume unit of cell (NVen), 131 vesicles/microns3; vesicular load of each cell front (N/S)b, 196 vesicle/microns2, and (N/S)i, 181 vesicles/microns2. The number of vesicles per volume unit (NVen) is smaller than that which has been described for systemic capillaries.

Evidence suggests that adenosine modulates neuronal and cerebral vascular functions by interacting with specific receptors on brain cells and blood vessels. Adenosine and other nucleosides are also transported across the blood-brain barrier via a saturable, carrier-mediated mechanism. Using direct ligand binding methods, we studied the two adenosine receptor subtypes, A1and A2, and the nucleoside transporter moiety in human brain microvessels, pial vessels, choroid plexus, and cerebral cortex membranes. The following specific tritiated ligands were used: cyclohexyladenosine (CHA) for A1receptors; 5'- N-ethylcarboxamide adenosine (NECA) for A2receptors; nitrobenzylthioinosine (NBMPR) and dipyridamole (DPY) for nucleoside transporters. We find that cerebral microvessels, pial vessels, and choroid plexus have few, if any, A1receptors, in contradistinction to cerebral membranes, which have a 10–20-fold higher density of A1receptor sites. Specific high-affinity NECA binding to A2receptors in cerebral microvessels, pial vessels, and choroid plexus was saturable and was equivalent to that of cerebral cortical membranes. The Bmaxand Kdof the high-affinity NECA binding to vessel preparations were ∼1.3 pmol/mg protein and ∼250 n M, respectively, which is similar to our previous findings in the rat and pig. NBMPR and binding were also saturable and were consistent with a single class of high-affinity binding sites. The density of nucleoside transporters was ∼four-fold higher in cerebral microvessels than in cerebral cortex, pial vessels, and choroid plexus. These results suggest that human cerebral microvessels have A2, but not A1, receptors and are particularly enriched with the adenosine transporter moiety.

Isolated intact, beating hearts were perfused with HPLC-pure [125]-IGF-I (1 ng/ml) alone or [125]-IGF-I (1 ng/ml) plus varying concentrations of unlabeled IGF-I (10-3,000 ng/ml) or unlabeled insulin (1,000-100,000 ng/ml). After 1 min of perfusion with peptides, the hearts were rapidly fixed, sectioned and analyzed for radioautographic [125I] grain counts. Greater than 90% of [125I] grains were shown to represent intact [125I]-IGF. Maximal grain counts over capillaries occurred after perfusion with [125I]-IGF-I alone and decreased in a dose-dependent manner when unlabeled IGF-I was coperfused. Coperfusion of [125I]-IGF-I with unlabeled insulin also decreased 125I grains over capillaries but less potently than unlabeled IGF-I. EM radioautography demonstrated that [125I]-IGF-I grains were localized over capillary endothelial cells. Thus, specific IGF-I receptors are present in the capillary endothelium of the intact heart and have properties similar to IGF-I receptors in cultured capillary endothelial cells.

Electron microscopy of citrate-phosphate-dextrose (CPD) buffered bank blood performed over 21 days shows that the normal architecture of erythrocytes, platelets and leucocytes disappears and that deformed organelles, leucocyte "ghosts", cell fragments and microaggregates accumulate. Leucocytes and platelets emerge as the most sensitive indicators of blood deterioration showing profound morphological changes from the first day. Microaggregates which passed through a 20-micrometer high capacity transfusion filter were identified as platelet conglomerates, leucocyte "ghost" and platelet-leucocyte "ghost" coaggregates with diameters of 6--20, 20--30 and 30--40 micrometers respectively. Of these aggregates present in the filtrate, 62% fell into the size range of 20--40 micrometers. The composition of microaggregates varies with storage time, the platelet conglomerates appear first during or after Day 1, leucocyte "ghosts" after Day 5 followed by platelet-leucocyte "ghost" coaggregate formation. At this stage the number of intact leucocytes and platelets is reduced and the filtrate shows an abundance of leucocyte debris. Microfiltration would thus appear to reduce but not eliminate the danger of microembolism and damage to capillary endothelium.

Morphological and physiological studies indicate multiple routes for transport across capillary endothelium. However, the identification of the morphological counterparts of specific transport processes (or the assignment of specific transport roles to morphologically identifiable pathways) has been only partly achieved: the contribution of endothelial cell membranes to transport of water and small, lipid-insoluble molecules needs to be evaluated. The identification of the "small pore" pathway for water and lipid-insoluble molecules with the intercellular junctions still remains questionable. The contributions to total macromolecular transport of junctions, single vesicles (pinocytosis, cytopempsis), chains of vesicles, and fenestrae are not yet known.

Histological studies on plaice tissues revealed mononuclear phagocytes emigrating through capillary endothelium in response to bloodborne foreign erythrocytes, with a >50% increase in circulating leucocytes within 2 h. Despite this rapid influx of leucocytes, cellular accumulation during peritoneal inflammatory responses was significantly slower than in mammals. In vitro studies with chemotaxis chambers revealed that random leucocyte migration was enhanced in the presence of endogenous chemostimulatory substances (inflammatory exudate fluid and endotoxin-activated plaice serum) although directional migration was not demonstrated. It is suggested that, compared with mammals, the slower accumulation of teleostean leucocytes at sites of injury is not due to a locomotory defect but possibly results from lower levels of endogenous chemoattractants being generated.

The permeability of blood vessels of the modiolus, especially cochlear plexus, in rats and guinea pigs has been studied ultrastructually by tracer experiments with horseradish peroxidase (HRP). Extravasation of intravenously injected HRP spread into intercellular spaces, but not outside the cochlear plexus. The capillary endothelium showed fenestrae with single-layered diaphragm, high distribution of labelled pinocytotic vesicles and penetration of HRP through endothelial tight junctions. On the other hand, blood vessels within the modiolus except for the cochlear plexus did not allow to leak HRP.These findings suggest that tight junctions bordering the cochlear plexus play a role in a part of the blood-perilymph barrier, whereas other blood vessels within the modiolus themselves act as the barrier.

Blood-to-brain amino acid transport consists of at least two components: 1. a fast rate or early process, commonly measured by the intra-carotid bolus injection method and attributed to transport across the capillary endothelium and entry into the astrocytes, and, 2. a slow rate or later component measured over 2 to 15 minutes probably associated with exit from the astrocytes and entry into the neurons. Incorporation into brain protein is temporally related to the second process. In the present study the slow and fast rate transport components and the incorporation into brain protein of tyrosine (Tyr) and Valine (Val) was measured in young adult and aged male C57BL/6 mice. The results indicate that the fast rate transport component is unaffected by age while the rates of the slow process and protein turnover show an exponential decline most marked between 3 and 8 months of age. Changes in the relative incorporation of Tyr and Val suggest that brain protein metabolism is altered qualitatively as well as quantitatively in aging, in these animals.

Erst 50 Jahre nach der Erstbeschreibung des Blutkreislaufes durch Harvey wurde das Kapillarsystem - von Marcello Malpighi an der Froschlunge - als Verbindungsglied zwischen arteriellem und venosem Kreislauf entdeckt. Seither ist gerade dieses mikrozirkulatorische Netzwerk Gegenstand zahlreicher, morphologischer und physiologischer Untersuchungen gewesen. Mit zunehmender Verfeinerung der technischen Moglichkeiten der Morphologie wurde eine sehr detailgetreue Darstellung der anatomischen Verhaltnisse moglich. Soweit dies die zellulare Ultrastruktur betrifft, fand bisher vor allem das variationsreiche Erscheinungsbild des Endothels Berucksichtigung. Aufgrund neuerer Erkenntnisse mussen besonders auf diesem Gebiet verschiedene - auch funktionell bedeutsame - Interpretationen revidiert werden. Fur die vorliegende Arbeit werden - unter Verwendung mehrerer, sich erganzender, morphologischer Techniken - neue Befunde der endonasalen Mikrozirkulation zusammengestellt und -soweit vertretbar - in ihrem funktionellen Kontext interpretiert. Harvey (1628) was the first to describe the blood circulatory system. 50 years later, the capillary system was discovered by Marcello Malpighi as a link between arteries and veins. Since then, the microvascular network has been examined abundantly by means of various morphological and physiological techniques. During the last decades the development of the technical equipment enabled us to receive detailed informations on the structural and ultrastructural aspects of the vasculature and - particularly - the capillary endothelium. New electron microscopic investigations are likely to revise earlier functional interpretations on the behaviour of this special cell system. In the present study we combined our own morphological results on the endonasal microcirculatory system - using different morphological techniques - to interpret these anatomical finding under functional aspects.

In adult mammalian lungs pinocytotic vesicles (PV) play a role in macromolecular transport across endothelium. The time course of their development in fetal lungs was examined. Morphometric techniques were used to measure the relative capillary volume as percentage of lung volume. Mean diameter ( D ), numerical density (Nv), and endothelial fractional volume (Vv) represented by PV were determined in randomly selected capillaries, measuring 5.3–8.4 μm in diameter, from right upper (RUL) and left lower (LLL) lobes of lungs from fetal lambs ranging in gestational ages from 39 to 144 days. Three newborn lambs, 1 hr after birth, were also examined. There was a 20-fold increase in the volume density of capillaries during the period studied. The vesicular D ± SD was 739.6 ± 4.1 and 735.1 ± 2.8 A in RUL and LLL, respectively, and remained unchanged throughout gestation. By contrast, following a gradual increase in Nv from 24.7 to 65.1/μm3 in the glandular stage (39–85 days), there was a rapid rise in Nv during both canalicular (95–121 days) and alveolar (130–144 days) stages of development, reaching a final Nv of 254.8/μm3. In newborn lambs, 1 hr after birth, there was no significant change in Nv. There was a significant correlation between Nv and fetal age, but there was no difference in Nv between RUL and LLL at any time. Thus, a more than 10-fold increase in Nv of PV occurs in ovine pulmonary capillary endothelium during gestation, the biochemical and/or physiological basis of which remains to be determined. By contrast, observations made on coated vesicles indicate that Nv of these structures does not change with gestation.

Summary Rabbits sensitized by injection were exposed to an aerosol of Micropolyspora faeni. Death occurred rapidly, and the lungs were immediately fixed and examined. The unprotected animals presented an allergic alveolitis with capillary lesions in which the changes in the endothelium were associated with intravascular coagulation. Heparin completely protected the endothelium but did not prevent the coagulopathy; an anti-platelet serum abolished this latter element of the reaction. The authors conclude that the alveolitis. which persisted in all the cases, was a Type 1 allergic reaction linked to the liberation of the mediators of immediate hypersensitivity. The changes in the capillary endothelium are the consequence and not the cause of the intravascutar coagulation. This coagulation is independent of the Type 1 allergic phenomena and it appears to be responsible for the development of the fibrosing granulomata characteristic of “farmer's lung”.

THE INABILITY of certain materials to pass from the circulation into the parenchyma of the central nervous system (CNS) has been attributed to a special barrier surrounding the entire system—the blood-brain barrier. This barrier is not present around certain other tissue, such as muscle, as evidenced by the fact that the same material freely passes into them. Certain areas of the brain, however, such as the choroid plexus and the area postrema, do not show a blood-brain barrier.1-3In these regions, the capillary endothelium is quite different from the rest of the brain parenchyma in that the endothelial cells are fenestrated and peroxidase has been observed penetrating "diaphragmatic central channels of the pores."3Thus, it seems reasonable to consider that the endothelium of the brain is at least one structural seat of the blood-brain barrier. Indeed, in the case of the barrier to the tracer, horseradish peroxidase, passage

Extremely long villous processes projected from endothelium toward capillary canal was observed in the blood vessels of very malignant pulmonary carcinoma. Many of the villous processes appeared to be long enough to interconnect and to interwind each other, and some of them showed waving or rolling shape. There are numerous vesicles in various sizes within the capillary endothelium from which these processes are projected. A correlation between the rapid growth of lung cancer and these unusual findings is not known at present.

1. The walls of iris vessels in five human eyes were studied. 2. No fenestrae are present in capillary endothelium. 3. A several thousand A thick basement membrane is found in practically all vessels. The basement membrane is often multi-layered and its external limit irregular. 4. A distinct zone of thin collagen fibrils is present between the “inner” and “outer tube” in almost all vessels. 5. Membrane-bounded, moderately dense bodies about 0.3 μ in diameter are concentrated among the extracellular components of vessel walls. 6. Muscular tissue is scanty. 7. No elastic fibres are found.

1. Controversial problems in the histological study of the glomerular epi thelium have been reviewed in the light of observations made on the kidney of the rat with a new technique of silver impregnation. The new technique gives an elective stain of the glomerular epithelial cells („Deckzellen“). 2. The perinuclear cytoplasm (cell body) of the epithelial cells extends into long processes (stem, main branches) which ramify upon and between the glomerular capillaries and form an investment of regularly spaced ring-like filaments (annular arborisation) upon the capillary endothelium. 3. Further branching of the annular arborisation, leading to the formation of filaments which diminish in calibre to the limit of resolution by the light microscope, has been observed upon the capillary endothelium. 4. The term ‘dendrite’ is proposed for the entire branching process of a glomerular epithelial cell. 5. Photographic evidence is provided which confirms and extends the observations of v. Mollendorff (1927) and Bargmann (1929) and supports the analysis of the glomerular epithelium made by these authors against the criticism of Zimmermann (1933). 6. A modification of the silver technique reveals the presence of large Golgiapparatus in the cell bodies of the glomerular epithelial cells.

Experimental lead encephalo-myelopathy of the suckling rat is the signpost on the tortuous road of uncovering prolonged metabolic dysoxidosis as the major pathogenetic principle in lead encephalopathy and in the other porphyrinopathic encephalopathies. This principle rests on the specific skill of the capillary endothelium of the nervous system to act as regulator of the blood-brain and blood-spinal cord barriers and on the extreme susceptability of this skill to chronic metabolic dysoxidosis. This same pathogenetic principle lies at the root of a group of neurological diseases for which we propose the name “systembound dysoric encephalopathies”. In contrast to lead encephalopathy of the suckling rat, human lead encephalopathy does not belong to this group because of added hemodynamic disorders. Such disorders prevent a pathoclitic distribution of the lesions.

Pathologists and physiologists are agreed that the capillary endothelium is of high importance in the animal economy, though it is admitted that its functions are involved in much obscurity. With the immunologist, the primary difficulty is lack of physiological data which would enable him to start with the normal functions and to interpret abnormalities in the light of these. And it is obviously far from easy to plan experiments providing the sort of information the immunologist wants about the functions of endothelium as part of a living mechanism, in which parenchymatous cells, body fluids, and endothelial channels jointly participate.

Micropinocytotic vesicles in the endothelial cells of capillaries in the diaphragm were counted during indirect repetitive stimulation of the muscle at a frequency of 50/sec, after division of the phrenic nerve, and during natural contraction and relaxation of the muscle during respiration. Changes in the total number of vesicles and even more marked changes in the ratio between vesicles fixed to the plasma membranes and lying freely in the cytoplasm of the cells were discovered reflecting changes in transendothelial transport of materials. The method of fixation used may affect the state of vesicle formation.

The length of the free surface of the capillary endothelium in the soleus muscle of rats whose mobility was restricted for between 1 and 60 days was studied on electron micrographs of transverse sections through the capillaries. On the first day of the experiment the length of the free surface of the endothelial cells was increased by 1.6–1.8 times over the control. On the 30th–60th day of limited movement these changes were no longer significant.

Bacteria and many colloidal substances injected intravenously rapidly disappear from the blood stream. This is due chiefly to the phagocytic activity of the reticulo-endothelial system of the liver, spleen, lungs and bone marrow, where the foreign particles may be demonstrated within the cells. The endothelium of other organs such as the kidney, muscle and skin, normally lack this function. Experiments are here reported which demonstrate a temporary phagocytic acitivity of the capillary endothelium of the skin, following injury of various sorts. This activity appears almost immediately after the trauma and disappears within an hour, and constitutes, perhaps, the initial stage of inflammation.A rabbit that had previously been found allergic to certain bacterial filtrates was selected. Sterile filtrate of B. lepisepticum (0.2 mil.) was injected intradermally at hourly intervals along the previously shaved side of the animal. After 5 or more hours, erythema appeared at the sites first injected, while the mor...

Ultrastructure of osmiophilic bodies identified as lipofuscin granules occurring at extraneuronal sites in the brain tissue of both young and old monkeys was studied. The present work revealed that lipofuscin granules were detected normally in the neuroglia cells, phagocytic cells and pericytes surrounding the blood capillaries, as well as in the capillary endothelium. However, their presence in these sites was more marked in young animals. The findings presented in this report are strongly suggestive of the normal removal of lipofuscin from the nerve cells to the capillary endothelium, and suggest further that the phagocytic cells as well as the glia cells participate in this removal mechanism. Being a more active process during youth, few lipofuscin granules are present in neurones from young animals. Failure of the removal mechanism due to diminished activity of the participating cells with ageing, is probably the cause of lipofuscin accumulation in senescent neurones.